It is well known that alpha-olefins may be oligomerized to form poly alpha-olefins which are useful as lubricants, hydraulic fluids, and heat transfer agents. Various combinations of catalyst components have been described.
For example, Dupas et al. U.S. Pat. Nos. 3,634,249 and Sauer 3,113,167 show a combination of trialkylaluminum and titanium tetrachloride for making synthetic lubricating oils. The catalyst, prepared in a hydrocarbon solvent, is used for the copolymerization of ethylene and propylene. No organo-halide compound is present. Beynon et al., Polymerisation of Dec-1-ene, J. Appl. Chem., 12, Jan. 1962, describes the polymerization of decene using a catalyst combination of trialkylaluminum and titanium tetrachloride. Again, no organic halide is added and in both instances a very slow Ziegler catalyzed reaction occurs.
Loveless, in U.S. Pat. No. 4,041,098, oligomerizes straight chain olefins by forming a first feed containing a low molecular weight alpha-olefin and a soluble aluminum alkyl halide and a second feed containing alpha-olefin and an organic halide. He forms synthetic lubricating oils. No titanium halide component is present.
Bacskai, U.S. Pat. No. 3,251,901, illustrates the use of a three-component Ziegler catalyst system wherein a titanium compound such as titanium tetrachloride is admixed with a low molecular weight alkyl aluminum compound in an inert diluent to form the catalytic medium. Thereafter, the alpha-olefin monomer containing a small amount of allyl halide is contacted with the catalyst. The allyl halide is added in varying amounts to regulate the molecular weight of the product. The titanium tetrachloride and alkyl aluminum form a catalyst suspension which must be stirred during the reaction process. In the system described, the allyl chloride serves to reduce the viscosity of the product. Its behavior is apparently unique, since other organic halides such as carbon tetrachloride and n-propylchloride are found to have no effect.
Favis U.S. Pat. Nos. 3,472,910 and 3,549,723 make low molecular weight poly alpha-olefin polymers. The catalyst system described comprises an aluminum trialkyl, titanium tetrachloride, a tertiary alkyl halide or alkyl halo cyclopentane and ferrocene. Typically, the catalyst components are thoroughly mixed and heated to the reaction temperature in the reactor prior to the introduction of ethylene. In preparing the catalyst, the trialkyl aluminum and the chlorinated hydrocarbon are first reacted.
In Vandenberg U.S. Pat. No. 3,354,139, ethylene is polymerized to poly alpha-olefins with the addition of a halo-alkane to control the molecular weight. The catalyst components described are aluminum alkyl and titanium tetrachloride. As in the case of certain of the above references, the catalyst is formed by first admixing the aluminum alkyl and the titanium tetrachloride to obtain a suspension.
Ichikawa et al., in U.S. Pat. No. 3,717,613, while concerned with the preparation of copolymers such as acrylonitrile nitrile and butadiene of high molecular weight, shows a three-component Ziegler catalyst system comprising a trialkyl aluminum, an organic halogen compound, and a metal compound such as titanium tetrachloride. Here the catalyst is formed by first admixing the organic halogen compound with the transition metal compound, e.g. titanium tetrachloride, in a solvent and then adding the organo-aluminum compound to this admixture. Thereafter the monomers are brought into contact with the catalyst solution. The reaction, as is typical with the Ziegler type, is slow.
The use of multicomponent Ziegler catalyst systems for preparation of high molecular weight poly-olefins is shown in Miller et al. U.S. Pat. Nos. 3,432,513; Calfee 3,131,171; and McManimie 3,065,220. The Miller patent shows the production of polypropylene and teaches that the addition of an organic halide compound increases the amount of isotactic material produced. The preferred mode of addition of the catalyst components is to admix the organo-aluminum compound and the organo-halide in the inert diluent initially and thereafter to introduce the titanium halide. It is further disclosed that the first two compounds are preferably aged and in some cases heated before the titanium tetrachloride is added.
Calfee shows a catalyst system prepared by admixing a Ziegler catalyst with a solution of aluminum chloride in a lower alkyl halide. The Ziegler catalyst is formed by the reaction of a trialkyl aluminum with titanium tetrachloride. The purpose here is to obtain higher yields of solid high molecular weight polymer.
McManimie shows the use of Ziegler catalysts for making high molecular weight polyethylene. The catalyst is prepared by initially admixing the trialkyl aluminum with the titanium tetrachloride to form a catalyst suspension. To this extent, the disclosure of this patent is comparable to the Calfee patent.